Serenade
by bravevulnerability
Summary: 'Castle is a fan of gestures, especially those that tend to be grand, and she fully intends to give him one tonight. Not if he fails to show up, though.' A late season 4 one shot.


**A/N: After originally attempting to publish this story yesterday, I eventually decided to temporarily remove it due to trouble with the site causing it to frequently disappear. I apologize to any who this may have inconvenienced, but hopefully my second attempt at sharing this fic is a more successful one. Thank you to all who managed to read this upon its first appearance and sent me such kind words about it, I hope you don't mind seeing it in your inboxes once more.**

* * *

 **Set shortly after 4x17, Once Upon A Crime.**

* * *

The top row of her teeth stab into her bottom lip, piercing the enticing curve of an adorable smile that is always rare to make an appearance. And when that smile does appear, it's usually for him.

Castle watches with curiosity and a hint of jealousy as she grins down at the text on her phone before rising from her seat, the glance of her eyes flicking in the direction of the break room.

"Beckett?" he calls, pointing helplessly to the paperwork he's supposed to be watching her do, but Kate ignores him, striding into the break room and easing the door shut with the heel of her boot while she lifts the phone to her ear.

Castle huffs and pushes up from his own seat, craning his neck in an attempt to see through the tiny sliver of a crack the door provides. He catches a glimpse of Kate walking back and forth, pacing the length of the lounge area, and - and did she just twirl a strand of her hair around her index finger?

Rick sidesteps the edge of her desk, nearly slamming his hip into the sharp corner in his haste to be closer, to eavesdrop, and trots across the bullpen, trying to remain free from the sight of the slit blinds covering the break room's windows.

"No, really. I've been looking forward to this all week," he hears her voice float through the slit of space left between the door and the frame as he inches near, pressing his back flat against the wall and ignoring the strange looks he's currently receiving from the fellow officers and detectives roaming the floor. They should be used to his antics by now anyway. "Is seven still good?"

His heart is twisting in his chest even as his mind tries to reason with the wounded muscle, attempting to reassure him that there is no way she is talking about a date right now, that the shy smile gracing her lips is not because of a man, and that it doesn't matter if she's toying with a lock of her hair… even if it is one of her tells.

"Still at Simone's on West 3rd street, right?" she asks and Castle withdraws his phone immediately, types in the name of the establishment on his maps app. A jazz club? A perfect setting for a date. "Yeah, I know it's been awhile, but I feel like I'm ready to give it another shot."

His fingers tighten around the exterior of his phone, causing the case to creak under the pressure of his grip.

Since when is she _ready_?

"Okay yes, I'm excited too," she chuckles and the sound, so lovely and light, a sound that usually has his heart fluttering, is like a punch to his gut. "See you then."

Rick swallows hard, hastily retreats from his hiding spot, making a break for the elevators before she can emerge. Normally, he would let her know he was leaving, place a silly note on her desk or send a text to her phone, but any form of communication would be too much for him right now.

Because apparently, Kate Beckett is going on a date tonight. While they're supposed to be waiting. And his heart has been ripped to bitter shreds because of it.

* * *

Kate steps out of the break room with her heart pounding, her expression calm but her eyes searching for him with anticipation, eager to see his attempt at hiding his reaction to the conversation she _knows_ he just overheard.

But as her eyes scan the bullpen, lingering on his empty chair beside her desk, she finds no sign of him. It's nearing five and her shift has already come to a close, thankfully with no open cases still on her desk, and she only has two hours before she has to be at the club, but she had hoped to speak with him beforehand, ensure that he would show up. Castle is a fan of gestures, especially those that tend to be grand, and she fully intends to give him one tonight.

Not if he fails to show up, though.

"Hey, Mick, have you seen Castle?" Beckett calls to the detective walking past her desk.

The man pauses on his journey to the break room, empty coffee cup hanging in his fist as he nods.

"Yeah, he was lurking 'round the break room, but then I saw him head for the elevators, must've left." He shrugs. "Looked a bit upset too, tough case?"

"Something like that," Beckett murmurs, offering Mick an appreciative quirk of her lips for the information before allowing him to continue on his way.

Kate frowns and snags her jacket from the back of her desk chair, slipping it on - something that feels so foreign after allowing him to do the job for far too long now - and bending to grab her messenger bag from the bottom drawer of her desk.

He'll show, she reasons with herself on her way to the elevator, even if he may have somehow been upset by the snippets of the conversation he heard, his curiosity will still get the better of him and he'll be in the crowd tonight.

If not, she'll damn well bring her gesture to his doorstep.

* * *

He sulks until approximately 6:27, according to the time stamp on the upper righthand corner of his laptop, before he decides he's going. Even if she is on a date, even if she has apparently moved on without having the decency to let him know, even if it'll cause the stinging in his chest to intensify - Richard Castle is going to that jazz club to learn the truth, no matter how brutal.

With one more shot of whiskey for courage, Castle saves his work, though he's added no more than a single sentence to his latest draft of Frozen Heat, and closes his laptop.

"Hey there, kiddo," Martha sings, sashaying around his kitchen with a glass of white wine balanced in her dazzling fingers. "Off somewhere fun tonight?"

Castle scoffs under his breath and retrieves his coat from the closet. This is likely going to be anything but _fun_. "Something like that. Going to meet Beckett, actually."

His mother's eyebrows hitch with intrigue and he knows she wants the juicy details of what he's sure her mind is conjuring up to be some magnificent date night, but he's steadily running out of time.

"Sorry Mother, I'm in a bit of a hurry," he apologizes, earning a wave of dismissal in return.

"Fine, fine, but let me know beforehand if you'll be bringing Katherine back for the evening. I'll happily put on an encore of my last performance since I know how much she enjoyed it," his mother preens and despite the ache nestled beneath his ribcage, Castle has to bite back a laugh. Kate was incredibly gracious and offered copious amounts of praise to Martha for her endless tales of the struggles and triumph that come with motherhood, but he would never subject her to such a performance again. Willingly, at least. Though, he wouldn't mind the returning cover of her palm to his knuckles, the warmth of her fingers curling with his…

"Richard, weren't you saying you were going to be late?"

"Oh, yes," he murmurs, tugging the front door open and wishing his mother a good night.

"If I don't hear from you, I'll be sure not to wait up," Martha winks and as much as he'd like to smile, to have hope ignite in his chest at the implication, he can only manage a grimace in return.

* * *

He isn't here.

Kate smoothes a hand over the shimmery black fabric of her dress, attempting to soothe the disappointment in her stomach and calm the simmering nerves as the host steps on the dimly lit stage, informing the audience of her upcoming performance.

"Hey girl, you ready?" Lanie approaches with a radiant grin. Of course, her best friend had been _thrilled_ by her plan to lure Castle to the club, to 'serenade' him with a talent she didn't often share with others. But she had performed in the intimate setting of the jazz club Lanie's cousin owns before, a couple of times actually, and while never before has she sang for a crowd with someone other than her best friend as a familiar face in the small mass of people, she had been looking forward to sharing this with him tonight.

"He didn't come," Kate sighs, scraping a hand through her tousled curls. "I thought for sure…" She shakes her head, cursing herself for the stupid idea, for leaving him breadcrumbs instead of simply leading him to the club on her own. "Maybe this was a bad idea."

"Hey, it's still early," Lanie reminds her, reaching out to squeeze Kate's bicep. "Seriously, honey, he could show up at any minute. So stop worrying and prepare those vocal cords because it's showtime."

But he may not and after the description of his behavior, she feared Castle had somehow misunderstood the conversation, allowed the creative side of his mind to twist the words into a different meaning that somehow offended him.

"Lanie, I can't do this-"

The microphone is tapped to life once more and the host of the club is speaking again as Lanie shushes her insecurities and nudges her out of the shadows.

" _And now we welcome to the stage, the lovely Katherine Beckett_."

* * *

Castle pays the small entry fee to the cozy little jazz club on autopilot, his eyes already scanning desperately for Kate in the candlelit crowd of tables, but it isn't until his gaze finds the stage that he sees her.

His breath catches harshly in his ribs, arrested by the sight of her in a dress that clings to her lithe frame, ending above her knees to allow a glimpse of her long legs, the matching black stilettos he's seen her wear before, but never like this. Never with a beautiful black dress that glistens in the golden spill of low lights above the stage, never with her hair curled luscious and thick and her lips painted red.

And then she starts to sing and he really thinks he may pass out if he doesn't find a way to get oxygen in and out of his lungs properly.

She wasn't here for a date. She was here to perform.

 _I've got you under my skin, I've got you deep in the heart of me,_

 _So deep in my heart that you're really a part of me…_

He's standing at the back of the club, dazed, but manages to draw closer to the stage, lured by the sultry melody of her voice, the husky undertones and effortless caress of the notes of Sinatra from her tongue. Castle makes it halfway through the maze of tables before her eyes finally land on him, blooming gold as her voice nearly hitches over the chorus, but she recovers quickly, without issue.

He doesn't.

Kate pins him to the spot without moving from her place in the middle of the stage, her fingers still curled around the microphone stand, but her gaze on him, as if every word is _for_ him.

 _But each time I do just the thought of you, makes me stop just before I begin, cause I've got you under my skin._

Her eyebrows arch with the lyrics, the gorgeous line of her mouth curling into a smile.

 _Yes, I've got you under my skin._

"Where the hell have you been?"

Castle startles at the hiss of Lanie's voice in his ear, again at the sudden applause that he swiftly joins in on, ignoring Lanie's question for another second to admire the stunning image of Kate on the stage again, bashful and lovely, blushing beneath the warm lights when he grins at her.

"If you would have been here on time, she would have dedicated the damn song to you instead of just having eye sex with you the entire time," Lanie mutters while the rest of the club begins to quiet back to the normal, low hum of activity as Kate makes her descent from the small stage, waving her thanks to the band.

"Wait, dedicate the song to me?" he echoes, turning bewildered eyes to the smirking M.E at his side. "She was - that was for _me_?"

"Don't get a big head about it," Lanie warns, poking a finger into his shoulder, but he barely feels the sharp stab of her nail. Not when Kate Beckett just sang to him and is now watching him with invitation in her eyes from the shadows of stage left.

"I won't," he promises Lanie distractedly, but Beckett's best friend is already shoving him from the clusters of tables.

Rick stumbles but finds his footing, trots over to the gorgeous detective with the voice of an angel waiting for him, and attempts to come up with the words adequate enough to express how in awe he continues to be of her.

"Hey Castle, I was wondering if you'd show," she murmurs once he finally reaches her in the candlelit corner of the club. "Want to sit?"

Kate nods towards a nearby booth that he has a feeling Lanie's managed to keep empty for them this entire time. Beckett doesn't wait for his answer to step past him, sliding into the leather seat and watching him over her shoulder with a grin as he scrambles to join her.

"That was amazing," he blurts the moment he sits down beside her and he almost expects an eye roll, but the soft smile on her lips grows, the gentle blush on her cheeks darkening a shade.

"Yeah?"

"Duh, Beckett," he huffs, scooting in a fraction closer than she would normally allow. But she doesn't stop him this time. "Your voice is beautiful. But I guess I shouldn't be surprised if our quintet of _Piano Man_ last year was any indication."

She shakes her head, laughing quietly and causing her hair to spill over her shoulders, and Castle reaches forward, brushes the curtain of chestnut curls back with his hand, grazing the bare edge of her shoulder with his fingertips.

"You wanted me to be here tonight?" he asks, remembering Lanie's comment amidst the haze of her presence, the lingering effects of her voice and the certainty in her gaze that has never quite been there before tonight. "You knew I was listening in on your conversation earlier?"

Kate sighs and leans back in the booth. "Yeah, I had been talking to Lanie on the phone when I felt you creeping at the door. I figured hearing me talking about a jazz club would be enough to get you here."

"It was," he assures her on a chuckle, propping an elbow on the dark marble of the tabletop. "But this entire time I thought - I think I heard your end of that conversation all wrong."

Kate's brow furrows as she sits up. "How?"

"Well," Castle shifts, briefly directing his gaze to the knot of his nervous fingers on the table. "I thought you were talking to someone else. Someone you might be seeing. About meeting here… for a date."

Silence is his only response and Rick hesitantly lifts his eyes to her face, finding her watching him with a mixture of remorse and apology that he never would have anticipated, that he doesn't necessarily like.

"That's why you disappeared today, why you were upset," she murmurs, stating facts and putting pieces together like she would for a case before pressing two fingers between her brows and squeezing her eyes shut in a gesture he recognizes as self-irritation.

"Kate, it's not a big deal, I just misunderstood-"

"No," she interrupts, her voice firm. "Castle, I - I would never… I don't want anyone else."

"You - you don't?" he repeats, his tongue heavy and awkward in his mouth, his heart a loud, fumbling thing in his chest.

Her brow creases deeper at the disbelief in his voice he failed to hide. "Rick, when I talked about being ready for a relationship at the swings, I was… I was talking about a relationship with _you_. I wouldn't put in the work for anyone else." Her eyes lower sheepishly. "I was hoping this… this could be my way of telling you that I didn't want to wait anymore, that I wanted more. With you."

His mind is spinning, memories of the impending heartbreak he felt swaying beside her on a swing set earlier in the fall reappearing in his chest, her words from that day echoing in his head, and all of the moments since then, the fleeting brushes of her hand, the soft smiles she reserved for him and him alone, the tenderness that blossoms in her eyes every time he shows up at the precinct or to a crime scene - they flare bright in his brain, supporting her claims.

She has been trying, for him, for them, and he had so little faith, he thought she had been meeting here with another man tonight, replacing him.

"I don't want anyone else," she states again when he fails to speak, forgets how as one of her hands rises to his face, tentative fingertips grazing his cheek, catching at his chin. "I just want you."

"You already have me," he murmurs, relieved when the words come out only slightly breathless, thrilled when they bring a gentle smile to her lips. "Under your skin, apparently."

Her laugh breaches the intimacy of the moment, but Kate nods, surprising him further when her head tilts forward, the soft skin of her forehead smearing a kiss to his. "Yeah, so what are you going to do about it?"

Castle's eyebrows hitch against hers in response, arousal simmering like lava in his blood, and her eyes are already slipping shut, grazing along his mouth before her lashes kiss her cheeks. Pure unabashed invitation that Castle takes.

His head tilts as his palm lifts to her cheek, cradling the slash of bone while his lips brush over hers once, eliciting a stuttered breath that bathes the flesh of his mouth in heat and anticipation, and then he's kissing her, savoring the perfect fit of her mouth and the low hum of satisfaction she emits when he sucks her bottom lip into his mouth.

"Cassandra, pop some champagne! I just won three hundred dollars!"

Their kiss is broken by the huff of Beckett's laughter, her lashes tangling with his as her eyes roll at Lanie's gleeful exclamation from across the club.

"That pool's still going?" he mutters, stroking his thumb along the delicate skin beneath her eye.

"Oh yeah," Kate chuckles, her arms coiling loose and wonderful around his neck, her fingers combing through the fine hairs at the base of his skull, leaving him breathless, because he had expected his heart to be broken tonight and instead, it thrives wild and swollen with joy in his chest. "A good thing about it though?"

"Hmm?" he murmurs, dreamily. He couldn't care less about bets the entire precinct has been making on them for the last four years. He has Kate Beckett's arms around him, the taste of her on his tongue, and her smile glancing against his lips. Wanting him.

"I put a hundred on us."


End file.
